1. Field of the Invention
The present invention relates to a solid-state imaging device, which is an example of a semiconductor device for detecting a physical quantity distribution, and an imaging apparatus. More specifically, the present invention relates to a mechanism that is formed by arraying plural unit components, which have sensitivity to electromagnetic waves inputted from the outside such as light and radiations, and outputs an electric signal indicating a physical quantity distribution converted into an electric signal by the unit components to the outside.
2. Description of the Related Art
In recent years, as examples of a solid-state imaging device, image sensors of a MOS (Metal Oxide Semiconductor) type and a CMOS (Complementary Metal-Oxide Semiconductor) type that can overcome various problems of a CCD (Charge Coupled Device) image sensor attract attention.
For example, the CMOS image sensor has, for each of pixels, an amplifier including a floating diffusion amplifier. In reading out a pixel signal, as an example of address control, a system of a so-called column parallel output type or column type is often used. This is a system for selecting one row in a pixel array section, simultaneously accessing pixels for the one row, and reading out pixel signals from the pixel array section in row units, i.e., all the pixels for the one row simultaneously and in parallel.
In the solid state imaging device, a system for converting an analog pixel signal read out from the pixel array section into digital data with an analog digital converter (an AD converter) and, then, outputting the digital data to the outside may be adopted.
The same applies to the image sensor of the column parallel output type. Various signal output circuits have been devised as a signal output circuit for the image sensor. As an example of a most advanced form of the image sensor, an image sensor of an AD conversion system that includes an AD converter for each of columns and extracts a pixel signal to the outside as digital data has been proposed (see, for example, JP-A-2005-347932).
As the AD conversion system, various systems have been devised from the viewpoints of a circuit size, processing speed (an increase in speed), resolution, and the like. As an example, there is an AD conversion system of a so-called slope integration type or ramp signal comparison type (in this specification, hereinafter referred to as reference signal comparison type). This is a system for comparing an analog unit signal and a so-called ramp-shaped reference signal (a ramp wave), a gradual value of which changes, for converting the unit signal into digital data, performing count processing in parallel with this comparison processing, and acquiring digital data of the unit signal on the basis of a count value at a point when the comparison processing is completed. JP-A-2005-347932 also discloses an example of an image sensor adopting the AD conversion system of the reference signal comparison type.